This invention relates to the testing of electronic parts. More particularly, the invention relates to the electrical testing of electronic automotive components.
Two very important automotive components falling within the scope of the present invention are alternators and voltage regulators. The typical alternator is a three-phase, Y-wound unit with a six-diode rectifier. Current is supplied to the rotor (rotating field) through slip rings. When the automotive vehicle is inoperative, the field is disconnected from the battery either by opening the ignition switch or by opening field-relay contacts. The six-diode rectifier changes the alternating current to the direct current required by the vehicle electric system.
A typical voltage regulator has two sets of contacts, lower and upper. At intermediate speeds, the lower contacts open and close, inserting and removing a resistance in the alternator field to provide voltage-limiting action. At higher speeds, the resistance is not sufficient to hole the voltage down. As the voltage increases, the upper contacts begin to make and break contact. When the contacts close, the alternator field is grounded by the contacts. With both ends of the field grounded, additional regulation is achieved.
The alternator has a field relay which connects the alternator field to the battery when the ignition switch is closed; and disconnects the field from the battery when the ignition switch is opened, thereby shutting off the engine. This technique keeps the battery from discharging through the alternator field. An indicator light comes on when the ignition is first turned on, to indicate that the alternator is not charging. As soon as the alternator begins to charge the battery, the alternator voltage closes the field-relay contacts. With both sides of the indicator light connected to the insulated terminals of the battery, the light goes out, indicating that the alternator is charging the battery.
A more comprehensive description, including wiring diagrams, of automotive alternators and voltage regulators is contained in the McGraw-Hill Encyclopedia of Science and Technology, vol. 1, pp. 323-324, and vol. 14, p. 420. Said portions of the McGraw-Hill Encyclopedia are hereby incorporated by reference.
The present state of the art requires the dissassembly and testing of individual parts of alternators and voltage regulators when preliminary on-line tests fail to pinpoint the source of the defect or trouble spot. The disassembling and piece-by-piece testing of the parts is time-consuming and inefficient. Moreover, the test devices used are diverse, and the methodology requires a substantial background of technical experience and judgment. It would be greatly beneficial to have a simple inexpensive device for detecting and pinpointing defective parts of electronic automotive components without the necessity of disassembling the components and testing each part individually and separately.
Furthermore, it would be highly desirable to provide test apparatus which could be used by unskilled personnel, and in particular by the handicapped. Specifically, it would be of great benefit to industry and to society to have available test equipment which could be used by persons who are blind or deaf.